Actually that intuition freeze bug has been around since the first version of AmigaOS.( I seen it in 1.3 and still in 3.9bb2)
It also happens with a fresh install of os3.1 or 3.9+bb1+bb2
I bugged developpers alot about this bug of AmigaOS. They told me intuition had to be written from stratch to fix this. And some other told me to stop using patches even though I told them it happens even on a fresh install.
To reproduce this bug two intuition actions have to be executed at exactly the same time (milisecond?) And if you`r using your computer as fast as me.(switching screens opening windows,menus,etc...) this lock happens a lot.
TRY IT:
Assuming you have OS3.9+bb2
open a program that does open its own screen. By opening a AWeb on its own screen you are more likely to see this bug. And as soon as Aweb starts loading,(before screen is opened) start clicking on that popup gadget of AmiDock like a maniac. You have to slick on it very fastly. 10 or 20 times a second maybe. And as soon as Aweb screen opens your machine will freeze.